Ext.grid.GridPanel不需按住Ctrl键单元行多选效果实现

/*
    重写handleMouseDown方法实现不用按住ctrl建多选
*/
Ext.override(Ext.grid.CheckboxSelectionModel, {  
    handleMouseDown : function(g, rowIndex, e){    
      if(e.button !== 0 || this.isLocked()){    
        return;    
      }    
      var view = this.grid.getView();    
      if(e.shiftKey && !this.singleSelect && this.last !== false){    
        var last = this.last;    
        this.selectRange(last, rowIndex, e.ctrlKey);    
        this.last = last; // reset the last    
        view.focusRow(rowIndex);    
      }else{    
        var isSelected = this.isSelected(rowIndex);    
        if(isSelected){    
          this.deselectRow(rowIndex);    
        }else if(!isSelected || this.getCount() > 1){    
          this.selectRow(rowIndex, true);    
          view.focusRow(rowIndex);    
        }    
      }    
    }  
});